POST UTME AFE BABALOLA UNIVERSITY 2021 Chemistry | Objective

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Question 1 View Details
A 2.00 g sample of a polymer is dissolved in 50.0 mL of a solvent. If the density of the solution is 1.05 g/mL, what is the molar mass of the polymer?
A. 1000 g/mol
B. 2000 g/mol
Correct C. 5000 g/mol
D. 10,000 g/mol

Correct Answer: C

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Question 2 View Details
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO(g)?
A. -110.5 kJ/mol
Correct B. -110.5 kJ/mol
C. -110.5 kJ/mol
D. -110.5 kJ/mol

Correct Answer: B

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Question 3 View Details
A 1.00 L sample of a gas at 25°C and 1.00 atm is compressed to 2.00 atm at cons\tant temperature. What is the final volume of the gas?
A. 0.50 L
B. 1.00 L
Correct C. 2.00 L
D. 4.00 L

Correct Answer: C

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Question 4 View Details
The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. What is the s\tandard enthalpy of formation of H2(g)?
A. 0 kJ/mol
Correct B. 0 kJ/mol
C. 0 kJ/mol
D. 0 kJ/mol

Correct Answer: B

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Question 5 View Details
A 2.00 g sample of a polymer is dissolved in 50.0 mL of a solvent. If the density of the solution is 1.05 g/mL, what is the molar mass of the polymer?
A. 1000 g/mol
B. 2000 g/mol
Correct C. 5000 g/mol
D. 10,000 g/mol

Correct Answer: C

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Question 6 View Details
In the electrolysis of a solution of copper(II) sulfate, what is the primary product at the cathode?
Correct A. Cu
B. Cu2+
C. H2
D. O2

Correct Answer: A

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Question 7 View Details
What is the major product of the reaction between 2-methylpropane and chlorine?
A. 2-chloro-2-methylpropane
Correct B. 2,2-dichloro-2-methylpropane
C. 2-chloro-2-methylpropane
D. 2,2-dichloro-2-methylpropane

Correct Answer: B

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Question 8 View Details
What is the s\tandard enthalpy of formation of CO2(g) at 298 K?
Correct A. -393.5 kJ/mol
B. -393.5 kJ/mol
C. -393.5 kJ/mol
D. -393.5 kJ/mol

Correct Answer: A

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Question 9 View Details
What is the major product of the reaction between ethene and HBr?
Correct A. 1-bromoethane
B. 2-bromoethane
C. 1-bromoethane
D. 2-bromoethane

Correct Answer: A

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Question 10 View Details
What is the s\tandard Gibbs free energy change for the reaction 2H2(g) + O2(g) → 2H2O(l) at 298 K?
Correct A. -237.1 kJ/mol
B. -237.1 kJ/mol
C. -237.1 kJ/mol
D. -237.1 kJ/mol

Correct Answer: A

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Question 11 View Details
A 0.1 M solution of a weak base, B, has a pH of 9.25. Calculate the value of Kb for the base.
A. 1.8 x 10^\( -5 \)
Correct B. 2.0 x 10^\( -5 \)
C. 2.5 x 10^\( -5 \)
D. 3.0 x 10^\( -5 \)

Correct Answer: B

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Question 12 View Details
A solution contains 0.1 M NaCl and 0.1 M Na2SO4. Calculate the total concentration of ions in the solution.
A. 0.2 M
B. 0.3 M
Correct C. 0.4 M
D. 0.5 M

Correct Answer: C

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Question 13 View Details
A 2.0 g sample of a polymer is dissolved in 100 mL of solvent. Calculate the molar mass of the polymer.
A. 500 g/mol
B. 600 g/mol
Correct C. 700 g/mol
D. 800 g/mol

Correct Answer: C

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Question 14 View Details
A redox reaction involves the oxidation of Fe2+ to Fe3+ and the reduction of MnO4- to Mn2+. Write the balanced equation for the reaction.
Correct A. \[ \text{Fe}^{2+} + \text{MnO}_4^- + 4\text{H}^+ \rightarrow \text{Fe}^{3+} + \text{Mn}^{2+} + 2\text{H}_2\text{O} \]
B. \[ \text{Fe}^{2+} + \text{MnO}_4^- + 2\text{H}^+ \rightarrow \text{Fe}^{3+} + \text{Mn}^{2+} + \text{H}_2\text{O} \]
C. \[ \text{Fe}^{2+} + \text{MnO}_4^- + 3\text{H}^+ \rightarrow \text{Fe}^{3+} + \text{Mn}^{2+} + \text{H}_2\text{O} \]
D. \[ \text{Fe}^{2+} + \text{MnO}_4^- + 5\text{H}^+ \rightarrow \text{Fe}^{3+} + \text{Mn}^{2+} + 2\text{H}_2\text{O} \]

Correct Answer: A

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Question 15 View Details
A 1.0 M solution of a weak acid, HA, has a pH of 4.25. Calculate the value of Ka for the acid.
A. 1.8 x 10^\( -5 \)
Correct B. 2.0 x 10^\( -5 \)
C. 2.5 x 10^\( -5 \)
D. 3.0 x 10^\( -5 \)

Correct Answer: B

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Question 16 View Details
Determine the number of moles of $\text{O}_2$ required to react completely with 3.0 moles of $\text{C}_2\text{H}_6$ according to the equation: $\text{C}_2\text{H}_6 + \frac{7}{2}\text{O}_2 \rightarrow 2\text{CO}_2 + 3\text{H}_2\text{O}$
A. 1.5 moles
Correct B. 2.1 moles
C. 3.0 moles
D. 4.5 moles

Correct Answer: B

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Question 17 View Details
A sample of $\text{CaCO}_3$ weighing 25.0 g is heated to produce $\text{CaO}$ and $\text{CO}_2$. If the mass of $\text{CaO}$ produced is 17.0 g, what is the mass of $\text{CO}_2$ produced?
A. 4.0 g
B. 6.0 g
Correct C. 8.0 g
D. 10.0 g

Correct Answer: C

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Question 18 View Details
The half-life of a radioactive subs\tance is 5.0 years. If 100.0 mg of the subs\tance is initially present, what is the mass of the subs\tance remaining after 20.0 years?
Correct A. 12.5 mg
B. 25.0 mg
C. 50.0 mg
D. 100.0 mg

Correct Answer: A

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Question 19 View Details
A solution containing 2.0 M $\text{NaOH}$ is mixed with a solution containing 1.0 M $\text{HCl}$. If 50.0 mL of each solution is used, what is the concentration of the resulting solution?
A. 0.5 M
Correct B. 1.0 M
C. 2.0 M
D. 3.0 M

Correct Answer: B

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Question 20 View Details
A 2.0 L flask contains 1.0 M $\text{CO}_2$ at 25°C. If 1.0 L of $\text{N}_2$ is added to the flask, what is the new partial pressure of $\text{CO}_2$?
A. 0.5 atm
B. 1.0 atm
Correct C. 1.5 atm
D. 2.0 atm

Correct Answer: C

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Question 21 View Details
A 2.5 g sample of a metal carbonate is heated to produce a metal oxide. If the mass of the metal oxide is 2.0 g, calculate the percentage yield of the metal oxide.
A. 80%
B. 85%
Correct C. 90%
D. 95%

Correct Answer: C

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Question 22 View Details
A solution of sodium hydroxide (NaOH) is prepared by dissolving 25.0 g of NaOH in 250 mL of water. What is the molarity of the solution?
A. 0.5 M
Correct B. 1.0 M
C. 1.5 M
D. 2.0 M

Correct Answer: B

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Question 23 View Details
A 10.0 mL sample of a solution containing 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after the titration?
A. 7
B. 8
C. 9
Correct D. 10

Correct Answer: D

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Question 24 View Details
A 2.0 g sample of a metal is heated in air to produce a metal oxide. If the mass of the metal oxide is 2.5 g, calculate the percentage increase in mass.
A. 10%
B. 20%
Correct C. 30%
D. 40%

Correct Answer: C

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Question 25 View Details
A solution of sodium carbonate (Na2CO3) is prepared by dissolving 50.0 g of Na2CO3 in 500 mL of water. What is the molarity of the solution?
A. 0.5 M
Correct B. 1.0 M
C. 1.5 M
D. 2.0 M

Correct Answer: B

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